Calculators:

Information:

Welcome to our new and updated site. Browsing through the site you will find information on mass and liquid measurement as well as discussions on many of the latest consumer measurement issues. Take a look at our ever popular and expanding calculators & conversion sections.

We have just added sections on calibrating open neck provers and made available our Gravimetric Proving Worksheet. Also now available is the H2O density reference book and an open neck proving worksheet. There is so much to see, please look around and don't hesitate to contact us with your comments or to enquire about your custom metrology software needs.

Come back often as we are still editing daily and there will always be lots of new information. Please drop us an email and let us know what you think.

Positive Displacement (PD) Meters

PD meters are classified as direct measurement meters (as opposed to inferential meters). This is because they operate on the principle of volumetric flow measurement by segmenting
the flowing stream into distinct portions and providing an output directly proportional to the number of portions which pass through the meter.

In a positive displacement (PD) meter, the product which is being driven through the meter is forced to drive the measuring system directly. This system is usually designed as
a series of vanes, rotors or pistons which displace a given amount for each revolution. The drive train is then coupled (usually through a calibrator) to either a mechanical gear
head, or more commonly to a pulser(s) which convert the rotation into a series of electrical pulses which are then fed to an electronic register which converts the pulses into
a volume indication.

PD meters are available in several common designed, including the following:

Rotary Vane

Rotating Disk

Nutating Disk

Oscillating Piston

Sliding Vane

Oval Gear

Bi-Rotor

Rotating Paddle

as well as many others

PD meters are probably the most widely used meters in the petroleum maesurement fields. They have proven to be reliable and cost effective methods for measuring volumetric flow.

They do however have some weaknesses. One potentially severe limitation of PD meters is that, regardless of design, they rely on the product being measured to provide lubrication.
This is adequate in several applications, but has proven to be a limiting factor in others, most notably the measuremnt of very dry products such as LPG. PD meters are also subject
to variations in performance due to several other factors including meters size, product pressures, product compatability, product temperature, ambient temperature, product viscosity
product contamination and, in some cases, installation orientation.